The sampling technique known as dried blood spotting (DBS) was developed by the microbiologist Robert Guthrie in 1963. The sample collection procedure is simplistic, involving the collection of a very small volume of blood from a small incision to the heel or finger. A drop of blood is then directly applied to a sampling paper and dried for future analyte extraction. DBS sampling is now a common and established practice for the quantitative and qualitative screening of metabolic disorders in newborns (Edelbroek, P. M., J. van der Heij den, and L. M. L. Stolk, Dried Blood Spot Methods in Therapeutic Drug Monitoring: Methods, Assays, and Pitfalls. Therapeutic Drug Monitoring, 2009. 31(3): p. 327-336).
Conventional sampling techniques employ plasma or serum as the biological matrix of choice for analysis. These techniques require large volumes of blood to be collected directly from the vein of a test subject. Conversely, DBS sampling requires substantially smaller sample volumes (microliters as opposed to milliliters) which allows sample collection in situations where collection in the traditional manner may be difficult and is now routinely applied to epidemiological studies, and for example has been successfully implemented for assaying numerous biological markers such as amino acids (Corso, G., et al., Rapid Communications in Mass Spectrometry, 2007. 21(23): p. 3777-3784), and trace elements (Hambidge, M., Journal of Nutrition, 2003. 133(3): p 9485-9555).
DBS methodologies are particularly suitable for the analysis of infectious agents such as HIV and HCV, as the reduced sample volumes minimize the risk of infection and blood is no longer considered to be a biohazard once dried, which drastically simplifies the storage and transportation of samples (Allanson, A. L., et al., Journal of Pharmaceutical and Biomedical Analysis, 2007, 44(4): p 963-969). Without specialised storage requirements samples can be easily and cost effectively transported around the world. The technique affords a further advantage in that equipment such as centrifuges and freezers are not required for sample processing or storage.
DBS technologies have also been applied in pharmacokinetic analysis to analyse components in blood.
The medium currently used in DBS methodologies, which involves the drying and storage of blood and plasma samples prior to future extraction and analysis, comprises paper based cellulose materials. For example, modified paper based materials have been developed for simplified isolation of nucleic acid; where the paper is chemically treated with a range of compounds to promote the long term storage of DNA. However, paper based cellulose materials are not particularly suited to accelerated drying procedures, particularly with blood plasma, and are not suited to incorporating specific functionalities to facilitate selective extraction of components from blood.
There is consequently a need to identify alternative materials that provide properties for facilitating the drying and storage of biological samples including body fluids such as blood and plasma samples, for future extraction and analysis, or to allow specific functionality to be incorporated into the storage medium.